1. Field of the Invention
The present invention relates to fluid actuated shift bar housing assemblies for change gear transmissions and in particular relates to fluid actuated shift bar housing assemblies wherein a constant fluid bias is utilized to urge the shift bars into a first or neutral axial position, selectively applied fluid pressure is effective to urge a selected one of the shift bars into at least one second axial position for engaging a selected gear and a resilient detent means is porovided for retaining the selected shift bar in the gear engaged position in the event of a failure of fluid pressure to allow the vehicle or machine driven by the transmission to continue to operate in the engaged gear.
2. Description of the Prior Art
Shift bar housing assemblies wherein a plurality of axially movable shift bars, also known as shift rails and shift rods, each carrying or associated with a shift fork, are selectively axially moved to engage a selected transmission gear by axial movement of a clutch member, or of a gear carrying clutch teeth, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,105,395; 3,611,823, 4,152,949 and 4,194,410, all assigned to the assignee of this invention and all hereby incorporated by reference.
Fluid actuated shift bar housing assemblies, usually actuated by pressurized hydraulic fluid or pressurized air, and the controls therefor are also well known in the prior art as may be seen by reference to U.S. Pat. Nos. 2,924,111; 2,931,237, 2,932,371; 2,943,502; 2,943,719 and 2,974,766, all assigned to the assignee of this invention and all hereby incorporated by reference.
While the prior art fluidly actuated shift bar housing assemblies are generally satisfactory and are presently utilized, usually for remotely controlled and/or automatically controlled change gear transmissions, the prior art assemblies are not totally satisfactory as they were complicated and/or expensive to produce, install and/or service and/or they utilized springs or other means to center the shift rails in a neutral position which means tended to shift the transmission into neutral in the event of a loss of pressurized fluid which might undesirably render the driven device totally unusable.